Oxygen evolution reaction (OER) is the rate-controlling step of the electrochemical water splitting. The slow kinetics hinders large-scale H-2 production. Herein, the spinel NiFe oxides were prepared by directly pyrolyzing nickel hexacynoferrate precursors in air. The NiFe oxides were presented as mesoporous nanocubes with a specific surface area of 125 m(2) g(-1). The mesoporous spinel NiFe oxide nanocubes can afford a geometric current of 10 mA cm(-2) at a low overpotential of a 0.24 V and a small Tafel slope of 41 mV dec(-1) in alkaline solution. The specific activity can reach up to 0.37 mA cm(-2) with a turnover frequency of 0.93 s(-1). The superior OER activity of the NiFe oxide nanocubes (NiFeO NCs) can outperform those of the state-of-the-art IrO2 catalysts, and compare favorably with other spinel transition metal oxides reported recently under identical condition. NiFeO NCs also show a long-term durability without significant loss of the OER activity. Our works provide a new strategy to develop efficient, robust and earth-abundant spinel NiFe oxides as advanced OER electrocatalysts to replace the expensive commercial IrO2 catalysts for water splitting in the industrial scale. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.